In recent years, a demand for wireless communication using internet or the like even during moving is increasing. With increase of this demand, a demand for high speed wireless communication is also increasing. In such a situation, a portable telephone and a mobile terminal such as a smart phone, a tablet type personal computer, or the like which can perform high-speed packet communication are increasing.
As standards for realizing such high-speed packet communication, the various standards are proposed. As the specific examples, the standards for W-CDMA (Wideband Code Division Multiple Access), HSPA (High Speed Packet Access), LTE (Long Term Evolution), and the like are proposed. Each mobile terminal based on these standards can realize high-speed packet communication.
However, when the high-speed packet communication is performed, the power consumption of the terminal increases. Therefore, a problem occurs, in which the electric power stored in the battery is consumed at a high rate when a battery-driven mobile terminal performs the high-speed packet communication and time when the terminal can be used by a user at the time of going out decreases.
As a technology related to this problem, there is a technology to reduce the power consumption by performing a control such as setting an RRC (Radio Resource Control) state according to the communication state of the mobile terminal.
An example of the control method relating to RRC is disclosed in patent literature 1. In the technology disclosed in patent literature 1, at a normal condition, a state is set to a state wherein low speed communication is possible and only while packets are frequently received, a state is set to a state wherein high speed communication is possible. On the other hand, when no packet is received for a fixed time period, the state is changed from the state wherein low speed communication is possible to a temporarily stopped state. Thus, by setting the state to the temporarily stopped state, the power consumption can be reduced compared to a case in which the state wherein high speed communication is possible is always maintained. Further, because the state can be changed to the state wherein high speed communication is possible if needed, data can be received instantaneously. In the technology disclosed in patent literature 1, the RRC state is controlled in such a way and the power consumption of the communication terminal is suppressed totally.
According to the 3GPP (Third Generation Partnership Project) established by the communication standard standardization organization, the RRC state at the time of packet reception is standardized as follows (refer to non-patent literature 1 and non-patent literature 2).
In WCDMA (HSPA), a CELL_DCH (dedicate carrier channel) is allocated to a state wherein high-speed communication is possible, a CELL_FACH (forward direction access channel) is allocated to a state wherein low-speed communication is possible, and a CELL_PCH (paging channel) and a UTRA_Idle (Idle) are allocated to a temporarily stopped state. Here, the power consumption decreases in an order of DCH>FACH>PCH>Idle.
In LTE, an RRC CONNECTED (connection state, CONN) is allocated to the state wherein communication is possible and an RRC IDLE (Idle) is allocated to the temporarily stopped state.
Here, the power consumption decreases in an order of CONN>Idle.
Further, either communication based on LTE or communication based on WCDMA (HSPA) is selected on the basis of a type of a mobile network to which the mobile terminal is connected and circumstances of the moment. Further, in the communication based on these communication standards, the mobile terminal in the temporarily stopped state receives data has to change the state to the state wherein high speed communication is possible or the state wherein low speed communication is possible from the temporarily stopped state.
When the RRC state is changed, a negotiation is needed between a network device and the mobile terminal included in the mobile network. However, it takes a reasonable length of time to complete the negotiation because of a communication delay between the network device and the mobile terminal, a processing time in the network device and the mobile terminal, and the like. Namely, it takes a time to change the state of the mobile terminal from the temporarily stopped state to the state wherein communication is possible in which data can be received. Therefore, when the mobile terminal in the temporarily stopped state receives a reception request from the mobile network, it cannot start to receive the data immediately.
Further, as described in patent literature 1 and the like, when the mobile terminal in the state wherein communication is possible receives no packet for a fixed time period, the state of the mobile terminal is changed to the state wherein low speed communication is possible or the temporarily stopped state. However, a specific value of this fixed time period is determined by the mobile network or the mobile terminal in advance. Further, in the following explanation, a period required for changing the state from the state wherein communication is possible to the temporarily stopped state is called a “non communication transition preparation period”. The “non communication transition preparation period” may be generally called as the “inactivity timer length”.
On the other hand, a push type communication in which a service provider on the internet distributes an arbitrary message to the mobile terminal at an arbitrary timing starts to be used.
In the WWW (World Wide Web) used on the internet, the pull type communication in which a WWW server on the internet starts to communicate (mainly download) with the terminal by a trigger from the terminal is used. On the one hand, in the push type communication, the service provider's service server on the internet starts to communicate (mainly download) with the terminal by a trigger of a service server side. The push type communication is different in this point from the pull type communication.
Generally, the push type communication is individually installed for each application which provides a service. However, in recent years, from a viewpoint of network utilization efficiency, a general-purpose infrastructure is built as the push service. In this push service infrastructure, a push server or a server called a push proxy gateway (hereinafter, referred to as a “push server” including these servers) is installed in the network of the push provider. The push server receives a push request including a message (push message) to be pushed from the service provider and distributes the message to the mobile terminal on behalf of the service provider.
In patent literature 2, an example of such push server is described. An object of the technology described in patent literature 2 is to safely manage an identifier given to a portable terminal device in an information distribution system using a push notification service. In the technology described in patent literature 2, the identifier given to the portable terminal device is prevented from being leaked or made known by encrypting information in communication between the push server and the Web server included in the information distribution system.